Alkaline earth thiogallate and alkaline earth thioaluminate phosphors activated with europium are known in the art for both electroluminescent systems and phosphor converted LED systems. These materials can readily absorb the emission from blue, violet, or near UV emitting light sources such as the commonplace InGaN light emitting diodes. These typically green phosphor materials can be used independently to generate a green light, or they can be combined with other phosphor materials to generate white or other colored light. Similarly, these green phosphor materials may be combined, for example, with a blue or other LED and a red phosphor in order to generate the backlighting unit for a display, such as a mobile phone, tablet, laptop, monitor, or television.
In general lighting, it is often desirable to have a broad emission spectrum to improve the color rendering index or other quality of light metrics, such as CQS or TM-30-15. However, sometimes in lighting it is desirable to provide extra light in certain wavelength regions in order to accentuate certain features; for instance, grocery store display cases for beef may include extra light in the red region of the spectrum, similarly, spinach or green papers may appear more pleasing when the lighting provides extra light in certain green wavelengths.
In display backlighting, it is more desirable to have a narrow emission wavelength so that the color (a) appears more saturated and widens the green vertex of the color gamut, and (b) sustains fewer losses when passing through the green filter of a typical LCD filter system, because the majority of its intensity is well aligned with the highest transmissivity of the filter.